Medical balloon catheter

ABSTRACT

The medical balloon catheter of the present invention comprises a catheter shaft composed of a distal end shaft and a proximal end shaft and a balloon on the distal end of the distal end shaft, wherein the proximal end shaft is composed of a single member and the distal end portion of the proximal end shaft is lower in rigidity than the other parts thereof. The present invention also provides a medical balloon catheter having a structure in which a tube for passing a guidewire inside thereof is arranged so as to pass inside the balloon and the balloon and tube are fused together in the vicinity of the distal end of the catheter, wherein the ratio of the outer diameter of the small-diameter portion on the distal end side of the tube to the outer diameter of the proximal end portion is no less than 0.85.

TECHNICAL FIELD

[0001] The present invention relates to a medical balloon catheter usedfor medical applications, and more particularly to a medical ballooncatheter for percutaneous angioplasty (PTA : Percutaneous TransluminalAngioplasty, PTCA Percutaneous Transluminal Coronary Angioplasty, andthe like) during realization of peripheral angioplasty, coronaryangioplasty, valvular angioplasty, and the like.

BACKGROUND ART

[0002] Percutaneous angioplasty using medical balloon catheters has beenwidely used for dilation therapy of stenoses or blocked portions ofvascular cavities and for restoration or improvement of blood flow incoronary artery, peripheral blood vessels, and the like. In a typicalmedical balloon catheter, a balloon that can be inflated or contractedby internal pressure adjustment is joined to the distal end portion of acatheter shaft, and an inner cavity (guidewire lumen) for passing aguidewire and an inner cavity (inflation lumen) for supplying a pressurefluid for internal pressure adjustment in the balloon are provided inthe longitudinal direction of the catheter shaft inside thereof.

[0003] A typical example of PTCA technique using such a medical ballooncatheter is described below. First, a guide catheter is inserted fromthe punctured zone into a large femoral artery, brachial artery,scapular artery, and the like, and the distal end thereof is disposed inthe inlet of a coronary artery via the main artery. The guidewireinserted into the guidewire lumen is then advanced through the stenoticzone, and medical balloon catheter is inserted along the guidewire, andpositioned in the stenosis. A pressure fluid is then supplied to theballoon via the inflation lumen by using an indeflator or the like, anddilatotherapy of the stenosis is conducted by inflating the balloon.After the dilatotherapy of the stenosis, PTCA is completed bycontracting the balloon by pressure reduction and pulling it out of thebody. In the present example of technique, usage of the medical ballooncatheter for PTCA in coronary artery stenosis was described, but themedical balloon catheters have been also widely employed fordilatotherapy in body cavities and other vascular cavities such asperipheral vascular cavities.

[0004] Such a medical balloon catheter has a structure in which aballoon 2 is joined to the distal end of a catheter shaft 1, and a hub 3for supplying a pressure fluid for adjusting internal pressure in theballoon is joined to the catheter shaft 1. Based on the structure ofcatheter shaft 1, the catheters can be classified into two types.

[0005] The first type is the over-the-wire type (OTW type) in which theguidewire lumen 4 is provided from the proximal end side to the distalend side of the medical balloon catheter, that is, over the entirelength of the medical balloon catheter and a guidewire port is providedin the hub 3 (FIG. 1). The second type is the rapid exchange type (RXtype) in which the guidewire lumen is provided on the distal end side ofthe medical balloon catheter, and the guidewire port 5 is provided inthe middle part of catheter shaft 1 (FIG. 2).

[0006] A variety of characteristics are required from medical ballooncatheters. The main among them can be generally classified into thefollowing three groups: the ability to pass through the stenotic zone(crossability), the ability to follow the curved blood vessel(trackability), and the ability to transmit a force when the medicalballoon catheter is inserted into a blood vessel (pushability). Kinkresistance is an example of a characteristic relating to pushability.

[0007] Reducing the profile (thickness) of catheter shaft improvescrossability, but tends to degrade pushability and kink resistance.Further, increasing rigidity of catheter shaft improves pushability andkink resistance, but tends to degrade crossability. In other words, allthe above-mentioned characteristics are closely related to each other,and it is not easy to improve all the characteristics at the same time.Accordingly, a variety of techniques for improving crossability,pushability and trackability and increasing kink resistance have beendisclosed.

[0008] Examined Japanese Patent Application No. 5-28634 (Catheter)discloses a rapid exchange medical balloon catheter, in which an openingof the guidewire lumen is provided in the joining region of a mediumportion (distal end shaft in accordance with the present invention) anda base portion (proximal end shaft in accordance with the presentinvention) and when the guidewire is contained in the guidewire lumen,the catheter receives a continuous longitudinal support over the entirelength thereof.

[0009] Such prior art technology makes it possible to increase kinkresistance in a state in which the guidewire is contained in thecatheter, that is, inside the guide catheter. The drawback of thattechnology was that when the guidewire was inserted, the catheter couldbe easily bent in the joining region of the medium portion and baseportion and operation ability by the operator was very poor.

[0010] Japanese Patent No. 2933389 (Balloon Catheter Comprising InnerCavity for Guidewire on the Distal End Side) discloses a medical ballooncatheter in which a transition portion extending from the distal endside of the opening of the proximal end inner cavity of the guidewirelumen to the vicinity of the distal end of the first shaft portion(proximal end shaft in accordance with the present invention) has arigidity between that of the first shaft portion and second shaftportion (distal end shaft in accordance with the present invention).

[0011] This prior art technology provides a catheter shaft withincreased kink resistance, but this increase in kink resistance isimplemented by additionally providing the second shaft with a coil-likemember as a deformation preventing structure. The problem associatedwith such additional coil-like member was that the number of operationsduring catheter manufacture was greatly increased and, at the same time,the assembly method was made difficult which resulted in the increasedproduction cost. Further, with this prior art technology, thedeformation preventing structure was mounted on the outer or inner sideof the outer sleeve, or on the outer side of a core tube. When thedeformation preventing structure was mounted on the outer side of theouter sleeve, the increase in the outer diameter of the outer sleevecould degrade crossability, and when the deformation preventingstructure was mounted on the inner side of the outer sleeve or on theouter side of the cure tube, the inflation lumen was locally narrowed,producing an adverse effect on dilation or contraction behavior of theballoon.

[0012] Further, Japanese Patent Publication No. 6-507105 (VascularCatheter Comprising Guidewire Proximal End Cavity and IntermediateMember” discloses a vascular catheter comprising a main shaft (proximalend shaft in accordance with the present invention), a balloon, aplastic shaft portion (distal end shaft in accordance with the presentinvention) located between the main shaft and the balloon, anintermediate member mounted on the main shaft, extending inside theplastic shaft portion in the distal end direction and having a rigiditynot higher than that of the main shaft portion, and a guidewire lumen,wherein the guidewire inlet is withdrawn from the distal end of the mainshaft portion in the proximal end direction.

[0013] Such prior art technology provides a vascular catheter withimproved pushability and trackability and also increased kinkresistance. However, kink resistance demonstrated when the vascularcatheter is inserted into the guide catheter along the guidewire canhardly be considered good. In order to further increase kink resistance,it is necessary to enlarge the diameter of the core wire used as anon-rigid intermediate member. However, in order to ensure the effectiveinflation lumen, the increase in the profile of the catheter shaft isrequired, and the decrease in crossability and trackability causesconcerns.

[0014] Examined Japanese Patent Application No. 4-44553 (CatheterEquipped with Balloon) discloses a catheter equipped with a ballooncomprising a rigidity increasing member which extends in the axialdirection in the outer tube and provides it with rigidity and a portioncomprising no such rigidity increasing member at the distal end of heouter tube.

[0015] On the other hand, a balloon catheter is used to conductdilatotherapy mainly by inserting the catheter into the body passagewhich is the object of therapy and introducing the internal pressureinto the therapy zone. Therefore, the required mechanical propertiesinclude a strength sufficient to prevent rupture of the balloon when apressure necessary for the dilation is introduced and a capability tocontrol the balloon safely to the desired dilation size. Furthermore, inmost cases, in order to conduct therapy in a vascular system, thecatheter has to be inserted to the zone of pathology changes andprescribed position along the blood vessel and the operation ability ofthe distal end portion of the catheter for such an insertion is veryimportant.

[0016] The catheter is typically composed of thin tubular members andhas to be passed through the curved zones inside the body or narrowstenotic zones by operating the catheter from outside of the bodythrough the insertion opening into the body. Accordingly, a small sizeof the catheter itself, in particular, of the distal end thereof is veryimportant. In addition, a force applied to the catheter from outside ofthe body has to be effectively transmitted to the distal end portion andflexibility is required to adapt to the cured portions. Further, becauseguidewire is usually used by being passed inside the catheter, a smallfriction resistance between the catheter and guidewire is also animportant property allowing for smooth movement of the catheter withoutdisrupting the force transmission. In order to obtain such an operationability, the structure of a typical balloon catheter is required to havethe following properties: (1) flexibility of the distal end (far end)portion allowing the catheter to follow the curved internal passages,(2) strength of the proximal end (near end) portion sufficient toprovide for good transmission of force to the distal end, and (3) lowfriction and high sliding ability of the tube used for passing aguidewire in order to suppress friction resistance. Catheters satisfyingthose requirements are most often made of polyethylene, high-strengthpolyamide, or high-strength polyamide elastomers.

[0017] With respect to thinness and flexibility, a small size andflexibility of the balloon portion at the distal end of the catheter andin the vicinity thereof are the especially important properties.Furthermore, because this portion is often inserted into the curvedportions or slides over the softest portion of the guidewire insertedtherein, the absence of discontinuity in this flexibility is alsorequired. Thus, when the catheter is disposed in a curved portion, ifthe flexibility is discontinuous, bending of the catheter becomesdiscontinuous, and guidewire resistance in this portion greatlyincreases causing degradation of operation ability.

[0018] Further, a fixed portion of the tube for passing the balloon andguidewire is typically present as the distalmost portion “tip” at the deof balloon catheter. When this tip portion is hard, the difference inflexibility with the guidewire let out of the tip increases andguidewire can be easily bent in this zone, becoming a serious cause ofoperation ability degradation. Furthermore, in case of zone ofpathological changes with advanced calcification, the following effectsare of frequent occurrence. Thus, when an attempt is made to pass aballoon catheter along the guidewire that has been passed through such azone, if the distal end is not sufficiently thin, it is obstructed bythe hard zone of pathological changes and is not able to passtherethrough, or if the tip portion is hard, it is caught by the hardzone of pathological changes and is not able to pass therethrough.

[0019] Furthermore, in recent years, metallic stationary dilatorstypically called stents are often used in vascular dilation therapy. Inorder to conduct shape dilation after stent dilation (post-dilation) andalso in case of re-stenosis inside the stents and stenosis at the distalend side of the stents, the balloon catheter has to be passed inside thestents. However, in such a case, similarly to the zones of pathologicalchanges with advanced calcification, the problem was that if the distalend was not sufficiently small and the tip portion was hard, thecatheter was caught by the metallic stent and could not passtherethrough.

DISCLOSURE OF THE INVENTION

[0020] With the prior art technology described in the aforesaid openpublications, kink resistance was increased by using an outer tube withgood trackability that had a member increasing rigidity thereof.However, when the outer tube itself has a high kink resistance, or whena high kink resistance is provided with a reinforcing member such as ametal wire and the like disposed inside the outer tube, the rigidity ofthe outer tube is locally increased, but the kink resistance of theentire catheter shaft is difficult to increase. Further, the problemassociated with providing an additional component, as shown in theembodiment of the prior art technology in which a wire braid wasembedded in a plastic outer tube, is that the number of productionprocess operations was increased and production cost was raised.

[0021] This first problem can be resolved by providing a medical ballooncatheter which is easy to assemble and in which the rigidity of cathetershaft is caused to change continuously in the longitudinal direction ofthe catheter shaft and pushability and kink resistance are increased,while the profile of a catheter shaft is being held to a minimum andcrossability and trackability are being maintained.

[0022] The present invention based on the results of a comprehensivestudy conducted to resolve the aforesaid first problem provides amedical balloon catheter comprising a catheter shaft composed of adistal end shaft and a proximal end shaft, a balloon on the distal endof the distal end shaft, and a hub provided with a port for supplyingpressure fluid to the balloon on the proximal end of the proximal endshaft, wherein the distal end shaft comprises a guidewire lumen and aninflation lumen for dilating the balloon on the inner surface, theproximal end shaft is composed of a simple member and at the same timecomprises the inflation lumen on the inner surface, the distal endportion of the proximal end shaft has a rigidity lower than other partsof the proximal end shaft, and the distal end shaft and the proximal endshaft are joined together outside the distal end portion of the proximalend shaft. It is preferred that part of the distal end portion of theproximal end shaft overlap the guidewire lumen and that the distal endshaft have a rigidity lower than that of the distal end portion of theproximal end shaft. Further, the rigidity of the distal end portion ofsaid proximal end shaft may gradually decrease as the distal end side ofthe proximal end shaft is being approached.

[0023] A spiral notch is preferably provided on the distal end portionof the proximal end shaft. The pitch of the spiral in the spiral notchis preferably no more than 5 mm, more preferably, no more than 2 mm. Thepitch of the spiral may gradually increase as the distal end side of theproximal end shaft is being approached.

[0024] The width of the spiral in the spiral notch is preferably no lessthan 0.5 mm and no more than 10 mm, more preferably, no less than 0.5 mmand no more than 5 mm. The width of said spiral may gradually decreaseas the distal end side of the proximal end shaft is being approached.

[0025] Further, the pitch of said spiral may gradually increase as thedistal end side of the proximal end shaft is being approached and thewidth of said spiral may gradually decrease as the distal end side ofthe proximal end shaft is being approached.

[0026] Slits may be present on the distal end portion of said proximalend shaft instead of the spiral notch, and the slits can be presentalong either the axial direction or circumferential direction of theproximal end shaft. Further, grooves may be present on the distal endportion of said proximal end shaft instead of the spiral notch, and thegrooves can be present along either the axial direction orcircumferential direction of the proximal end shaft. Further, inaddition, holes may be present in the proximal end shaft instead of theabove-described notch, slits, and grooves.

[0027] The length of the distal end portion of the proximal end shaft ispreferably no less than 30 mm, more preferably, no less than 50 mm.

[0028] The proximal end shaft is preferably composed of a metal tube. Inthis case, the proximal end shaft is preferably composed of stainlesssteel, more preferably, of stainless steel SUS316.

[0029] Further, as described hereinabove, it is important that thedistal end portion of the balloon catheter, in particular, the portionfrom the tip portion to the balloon portion, be thin and flexible andhave no significant different in hardness with other portions of thecatheter. This is the second problem.

[0030] A method for adhesively fixing the balloon and the tube forpassing a guidewire inside thereof with an adhesive and a method forfixing by fusion are used as methods for processing the tip portion.When an adhesive fixing method is used, an adhesive layer is present. Bycontrast, with the method employing fusion, the adhesion layer is notpresent. In addition, the diameter can be easily decreased by thermalprocessing during or after fusion. Therefore, the fusion method iseffective in reducing the diameter, increasing flexibility, and reducingthe discontinuity of flexibility. However, in the conventionalcatheters, polyethylene, which is a polyolefin material, in particular,high-density polyethylene with an excellent low-friction characteristicwas most often used for the tube for passing a guidewire inside thereof(guidewire tube). High-density polyethylene is a material with excellentlow-friction characteristic, but has poor fusibility and adhesivebondability with other materials and cannot be fused to any materialsother than polyolefin materials. As a result, only adhesive bondingcould be used for joining it to other materials. On the other hand, whena balloon from a polyolefin material was used, fusion could be employed.However, because a bridge to the balloon was required, the portionserving as fusion tolerance restricted a possible reduction inthickness. As a result, the fusion process, too, could not provide forreduction of diameter and increase in flexibility of the tip portion.Furthermore, because the high-density polyethylene with excellentlow-friction characteristic has poor flexibility, the usage of alow-density polyethylene, which is a comparatively flexible material,for the guidewire tube has been considered. However, such a usage waspractically impossible because friction properties and slidingproperties rapidly degraded as the flexibility increased. When ahigh-density polyethylene single-layer tube was used as the guidewiretube, the tip portion was difficult to provide with sufficiently reduceddiameter and increased flexibility.

[0031] There are commercial balloon catheters in which a two-layer tubewith an outer layer from a polyamide and an inner layer of polyethyleneis used as the tube for passing the guidewire inside thereof and theballoon is made of the polyamide with properties identical to those ofthe polyamide of the outer tube. However, because the elastic modulus ofpolyamides is typically higher than that of polyethylene, the tipportion could not be provided with sufficient flexibility.

[0032] Further, there are commercial balloon catheters comprising aballoon made of a polyamide elastomer and a guidewire tube fabricatedfrom a polyamide elastomer with a hardness higher and melting point alsohigher than those of the polyamide elastomer of the balloon. However,because a material harder than the balloon was disposed in the guidewiretube, the tip portion did not have sufficient flexibility.

[0033] The second problem which is to be resolved by the presentinvention is to provide an improved medical balloon catheter which hasexcellent operation ability because the distal end portion of the distalend of the catheter has a sufficiently small diameter and sufficientlyhigh flexibility and also because the discontinuity of flexibility isreduced.

[0034] Means for resolving the second problem are provided by selecteddimensions, assembly method, and arrangement of materials.

[0035] Thus, the medical balloon catheter in accordance with the presentinvention is composed of a plurality of tubes and a balloon, thiscatheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in the tube are fusedtogether in the vicinity of the distal end of the catheter, wherein theratio of the outer diameter of the small-diameter portion on the distalend side in the tube to the outer diameter of the proximal end portion,(outer diameter of the small-diameter portion on the distal endside)/(outer diameter of the proximal end portion), is no less than0.85. With such a structure, the tip portion can be adjusted to aflexible state by increasing the flexibility of the guidewire tubeitself and by using fusion, which produces no adhesive layer, as afixing method, and the above-mentioned problem is resolved.

[0036] Further, the medical balloon catheter in accordance with thepresent invention is composed of a plurality of tubes and a balloon,this catheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in the tube are fusedtogether in the vicinity of the distal end of the catheter, wherein theShore hardness of the material constituting at least that part of thesmall-diameter portion on the distal end side in the tube which is fusedto the balloon is less than the Shore hardness of the materialconstituting the balloon. With such a structure, the tip portion can beadjusted to a flexible state by increasing the flexibility of theguidewire tube itself and by using fusion, which produces no adhesivelayer, as a fixing method, and the above-mentioned problem is resolved.

[0037] Further, the medical balloon catheter in accordance with thepresent invention is composed of a plurality of tubes and a balloon,this catheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in the tube are fusedtogether in the vicinity of the distal end of the catheter, wherein theflexural modulus of elasticity of the material constituting at leastthat part of the small-diameter portion on the distal end side in saidtube which is fused to the balloon is less than the flexural modulus ofelasticity of the material constituting the balloon. With such astructure, the tip portion can be adjusted to a flexible state byincreasing the flexibility of the guidewire tube itself and by usingfusion, which produces no adhesive layer, as a fixing method, and theabove-mentioned problem is resolved.

[0038] Further, the medical balloon catheter in accordance with thepresent invention is composed of a plurality of tubes and a balloon,this catheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in the tube are fusedtogether in the vicinity of the distal end of the catheter, wherein themelting point of the material constituting at least that part of thesmall-diameter portion on the distal end side in said tube which isfused to the balloon is lower than the melting point of the materialconstituting the balloon. With such a structure, the tip portion can beadjusted to a flexible state by increasing the flexibility of theguidewire tube itself and by using fusion, which produces no adhesivelayer, as a fixing method, and the above-mentioned problem is resolved.

[0039] Further, the medical balloon catheter in accordance with thepresent invention is composed of a plurality of tubes and a balloon,this catheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in the tube are fusedtogether in the vicinity of the distal end of the catheter, wherein theouter diameter of the small-diameter portion on the distal end side inthe tube is no more than 0.52 mm. With such a structure, the tip portioncan be adjusted to a flexible state by increasing the flexibility of theguidewire tube itself and by using fusion, which produces no adhesivelayer, as a fixing method, and the above-mentioned problem is resolved.

[0040] Further, the medical balloon catheter in accordance with thepresent invention has a structure in which the balloon is composed of apolyester elastomer material and at least that part of thesmall-diameter portion on the distal end side in said tube which isfused to the balloon is composed of a polyester elastomer material. Withsuch a structure, fusion which is used as the fixing method producing noadhesive layer is facilitated, the tip portion can be adjusted to aflexible structure with small discontinuity of flexibility, and theabove-mentioned problem is resolved.

[0041] Further, the medical balloon catheter in accordance with thepresent invention has a structure in which the balloon is composed of apolyamide elastomer material and at least that part of thesmall-diameter portion on the distal end side in said tube which isfused to the balloon is composed of a polyamide elastomer material. Withsuch a structure, fusion which is used as the fixing method producing noadhesive layer is facilitated, the tip portion can be adjusted to aflexible structure with small discontinuity of flexibility, and theabove-mentioned problem is resolved.

[0042] Further, the medical balloon catheter in accordance with thepresent invention has a structure in which the polyester elastomermaterial or the polyamide elastomer material has soft segments and hardsegments in a molecule and the ratio of soft segments in the materialconstituting the balloon is less than the ratio of soft segments in thematerial constituting the tube for passing a guidewire inside thereof.With such a structure, the flexibility of the guidewire tube itself isincreased, the tip portion can be adjusted to a flexible state, and theabove-mentioned problem is resolved.

[0043] Further, with the medical balloon catheter in accordance with thepresent invention, in addition to the above-described effects inherentto the aforesaid balloon catheter, guidewire slidability can beincreased by using a structure in which the innermost surface of thetube for passing a guidewire inside thereof is composed of high-densitypolyethylene.

[0044] Further, the medical balloon catheter in accordance with thepresent invention has a structure in which the tube for passing aguidewire inside thereof has a multilayer structure consisting of noless than two layers, the position which is to be fused is composed of apolyamide elastomer or a polyester elastomer, the innermost surface iscomposed of high-density polyethylene, and no less than one binder layeris present, if necessary, between the portion that has been fused andthe innermost surface. With such a structure, both the excellentguidewire slidability and the fusibility with the guidewire tube can beprovided and the above-mentioned problem is resolved.

[0045] Further, the medical balloon catheter in accordance with thepresent invention is composed of a plurality of tubes and a balloon,this catheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in said tube are fusedtogether in the vicinity of the distal end of the catheter, wherein thatpart of the small-diameter portion on the distal end side in the tubewhich is fused to the balloon is composed of a polyester elastomerhaving hard segments and soft segments in a molecule and the ratio ofthe soft segments is higher than 13%. With such a structure, the tipportion can be adjusted to a flexible state by increasing theflexibility of the guidewire tube itself and by using fusion, whichproduces no adhesive layer, as a fixing method, and the above-mentionedproblem is resolved.

[0046] Further, the medical balloon catheter in accordance with thepresent invention is composed of a plurality of tubes and a balloon,this catheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in said tube are fusedtogether in the vicinity of the distal end of the catheter, wherein thatpart of the small-diameter portion on the distal end side in the tubewhich is fused to the balloon is composed of a polyamide elastomerhaving hard segments and soft segments in a molecule and the ratio ofthe soft segments is higher than 14%. With such a structure, the tipportion can be adjusted to a flexible state by increasing theflexibility of the guidewire tube itself and by using fusion, whichproduces no adhesive layer, as a fixing method, and the above-mentionedproblem is resolved.

[0047] Further, the medical balloon catheter in accordance with thepresent invention has a structure in which the proximal end of an X rayimpermeable ring is abutted against and fixed to the boundary portion ofthe proximal end side and the small-diameter portion on the distal endside of the tube for passing a guidewire inside thereof. With such astructure, discontinuity of flexibility in the vicinity of the ballooncan be reduced and the above-mentioned problem is resolved.

[0048] Further, the medical balloon catheter in accordance with thepresent invention has a structure in which the tube constituting theouter surface of the catheter is composed of a material that can befused with the balloon and is fused and arranged on the proximal endside of the balloon. With such a structure, because no adhesive layer isformed, the distal end side of the balloon is flexible and discontinuityof flexibility can hardly occur therein. Therefore, the above-mentionedproblem is resolved. An additional advantage from the productionstandpoint is gained when the above-described structures are employed inballoon catheters of a rapid exchange type, in which the guidewire tubeis limited to a range from the distalmost end of catheter to theintermediate part of the outer tube, because the guidewire inlet portioncan be formed by fusing the outer tube with the guidewire tube, processstability is superior to that of the molding process using adhesivebonding or the like, and the diameter of this portion can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0049]FIG. 1 is a schematic perspective view of a catheter of anover-the-wire type, among the typical balloon catheters for PTCA;

[0050]FIG. 2 is a schematic perspective view of a catheter of a rapidexchange type, among the typical balloon catheters for PTCA;

[0051]FIG. 3 is a schematic side view illustrating a cross section of adistal end shaft with a coaxial structure in the rapid exchangecatheters which are the typical balloon catheters for PTCA;

[0052]FIG. 4 is a cross-sectional view along the A-A′ line in FIG. 3;

[0053]FIG. 5 is a schematic side view illustrating a cross section of adistal end shaft with a biaxial structure in the rapid exchangecatheters which are the typical balloon catheters for PTCA;

[0054]FIG. 6 is a cross-sectional view along the B-B′ line in FIG. 5;

[0055]FIG. 7 is a schematic side view illustrating a case where a spiralnotch is present on the distal end of a proximal end shaft in themedical balloon catheter in accordance with the present invention;

[0056]FIG. 8 is an expanded schematic side view of the spiral notchshown in FIG. 7;

[0057]FIG. 9 is a schematic side view illustrating a case where a partof the distal end of a proximal end shaft and an inner cavity forpassing a guidewire overlap in the medical balloon catheter inaccordance with the present invention;

[0058]FIG. 10 is a schematic side view illustrating a case where slitsare present in the axial direction on the distal end of a proximal endshaft in the medical balloon catheter in accordance with the presentinvention;

[0059]FIG. 11 is an expanded schematic side view of the slits shown inFIG. 10;

[0060]FIG. 12 is a schematic side view illustrating a case where slitsare present in the circumferential direction on the distal end of aproximal end shaft in the medical balloon catheter in accordance withthe present invention;

[0061]FIG. 13 is an expanded schematic side view of the slits shown inFIG. 12;

[0062]FIG. 14 is a schematic side view illustrating a case where groovesare present in the axial direction on the distal end of a proximal endshaft in the medical balloon catheter in accordance with the presentinvention;

[0063]FIG. 15 is a cross-sectional view along the C-C′ line in FIG. 14;

[0064]FIG. 16 is a schematic side view illustrating a case where groovesare present in the circumferential direction on the distal end of aproximal end shaft in the medical balloon catheter in accordance withthe present invention;

[0065]FIG. 17 is a cross-sectional view along the D-D′ line in FIG. 16;

[0066]FIG. 18 is a schematic side view illustrating a case where spiralgrooves are present on the distal end of a proximal end shaft in themedical balloon catheter in accordance with the present invention;

[0067]FIG. 19 is a schematic side view illustrating a case where holesare present on the distal end of a proximal end shaft in the medicalballoon catheter in accordance with the present invention;

[0068]FIG. 20 is a schematic side view illustrating a case where groovesare present in the circumferential direction on the distal end of aproximal end shaft and a core wire is provided in the medical ballooncatheter in accordance with the present invention;

[0069]FIG. 21 is a schematic view illustrating a system for evaluatingthe medical balloon catheter;

[0070]FIG. 22 is an expanded view of the curved plate shown in FIG. 21;

[0071]FIG. 23 is a cross-sectional schematic view illustrating thedistal end portion of the balloon catheter containing a balloon and atip portion of the balloon catheter in accordance with the presentinvention;

[0072]FIG. 24 is a cross-sectional schematic view illustrating thedistal end portion of the balloon catheter containing a balloon and atip port ion of the balloon catheter in accordance with the presentinvention;

[0073]FIG. 25 is a cross-sectional schematic view illustrating theentire rapid exchange balloon catheter in accordance with the presentinvention;

[0074]FIG. 26 is a cross-sectional view along the E-E′ line in FIG. 23and is a cross-sectional schematic view illustrating an example of thetip portion of the balloon catheter in accordance with the presentinvention;

[0075]FIG. 27 illustrates schematically a measurement system used forEvaluation 3 employed for demonstrating the effect of the presentinvention; and

[0076]FIG. 28 illustrates schematically a measurement system used forEvaluation 4 employed for demonstrating the effect of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0077] Various embodiments of the medical balloon catheter in accordancewith the present invention will be described below. First, theembodiments relating to a catheter shaft will be explained withreference to FIGS. 2 through 22.

[0078] The medical balloon catheter of the present embodiment has astructure in which, as shown in FIG. 2, a balloon 2 is joined to adistal end of a catheter shaft 1 and a hub 3 for supplying pressurefluid for adjusting the internal pressure of the balloon is joined tothe catheter shaft 1, and relates to a rapid exchange catheter in whicha guidewire lumen 4 is provided only at the distal end side of theballoon catheter and a guidewire port 5 is provided in the mediumportion of catheter shaft 1. The catheter shaft 1 of the presentembodiment is composed of a distal end shaft 10 and a proximal end shaft11 which are connected to each other in a joint zone 12. In this case,no limitation is placed on the structure of the distal end shaft 10, oncondition that the guidewire lumen 4 and an inflation lumen 6 areprovided therein. In other words, a coaxial structure may be employed inwhich, as shown in FIG. 3 and FIG. 4, an inner tube 7 and an outer tube8 are installed so that the distal end shaft 10 has a coaxialdouble-wall configuration and which has the guidewire lumen 4 demarcatedby the inner surface of the inner tube 7 and the inflation lumen 6demarcated by the inner surface of the outer tube 8 and the outersurface of the inner tube 7, or a biaxial structure may be employed inwhich, as shown in FIG. 5 and FIG. 6, the guidewire lumen 4 andinflation lumen 6 are arranged in parallel. Other structures also placeno limitation on the effect of the present invention. The referencesymbol 9 in the figures stands for a ring impermeable to X rays.

[0079] The proximal end shaft 11 is composed of a single member, and aspecific feature thereof is that the distal end portion 13 of theproximal end shaft 11 has a rigidity lower than that of the other partsof the proximal end shaft 11. No limitation is placed on means forreducing the rigidity of the distal end portion 13 of the proximal endshaft 11, and the rigidity of the distal end portion can be reduced byforming a spiral notch 14, slits 17, grooves 21, and holes 26. Theoptimum rigidity reduction means can be selected and implemented basedon the target profile or application of the medical balloon catheter,processing cost, and the like.

[0080] No limitation is placed on the method for forming the spiralnotch 14, slits 17, grooves 21, and holes 26, but from the standpoint ofprocessing accuracy, the formation method using a laser is preferred.The type of the laser to be used can be determined and selected bytaking into account the material of the proximal end shaft 11 and thelike.

[0081] When the rigidity of the distal end portion 13 of the proximalend shaft 11 is reduced with a spiral notch 14, as shown in FIG. 7 andFIG. 8, a pitch 15 of the spiral is preferably no more than 5 mm. Thepitch 15 of the spiral, as referred to herein, means the width of thenotch in the axial direction of the shaft (see FIG. 8). When the pitch15 of the spiral is greater than 5 mm, the rigidity of the proximal endshaft 11 decreases abruptly in the distal end portion 13, and theincrease in pushability and kink resistance, which is the object of thepresent invention, is difficult to attain.

[0082] Because the rigidity of the proximal end shaft 11 is determinedby the profile and material, the rigidity of the distal end portion 13of the proximal end shaft can be optimized by changing the pitch 15 ofthe spiral according to the application of the medical balloon catheter.With consideration for the profile required for the proximal end shaft11 when the medical balloon catheter is designed for PTCA, it ispreferred that the pitch 15 of the spiral be no more than 2 mm. When therigidity is thus optimized, a portion of the distal end of proximal endshaft 11 may overlap the guidewire lumen 4.

[0083] The pitch 15 of the spiral can be gradually increased as thedistal end side of the proximal end shaft 11 is being approached inorder to realize a medical balloon catheter in which continuousdistribution of rigidity in the entire catheter shaft is obtained due togradual reduction of rigidity of distal end portion 13 of the proximalend shaft 11 toward the distal end of the proximal end shaft 11 andwhich has even better kink resistance. In this case, the degree ofgradual increase in the pitch 15 of the spiral can be adjusted andoptimized by taking into account the rigidity of proximal end shaft 11and distal end shaft 10.

[0084] Further, when the rigidity of the distal end portion 13 of theproximal end shaft is reduced by the above-mentioned spiral notch, it ispreferred that the width 16 of the spiral be of no less than 0.5 mm andof no more than 10 mm. The width 16 of the spiral as referred to hereinmeans the width of the portion sandwiched between the notches in theaxial direction of the shaft. When the width 16 of the spiral is lessthan 0.5 mm, the rigidity decreases abruptly in the distal end portion13 of the proximal end shaft and the kink resistant is difficult toincrease. Furthermore, when the width 16 of the spiral exceeds 10 mm,the rigidity changes at the distal end side more abruptly than in theproximal end shaft 11 and the continuous distribution of rigidity isdifficult to realize.

[0085] Because the rigidity of the proximal end shaft 11 is determinedby the profile and material, the rigidity of the distal end portion 13of the proximal end shaft can be optimized by changing the width 16 ofthe spiral according to the application of the medical balloon catheter.With consideration for the profile required for the proximal end shaft11 when the medical balloon catheter is designed for PTCA, it ispreferred that the width 16 of the spiral be no less than 0.5 mm and nomore than 5 mm. When the rigidity is thus optimized, a portion of thedistal end of proximal end shaft 11 may overlap the guidewire lumen 4.

[0086] The width 16 of the spiral can be gradually decreased as thedistal end side of the proximal end shaft 11 is being approached inorder to realize a medical balloon catheter in which continuousdistribution of rigidity in the entire catheter shaft is obtained due togradual reduction of the rigidity of distal end portion 13 of theproximal end shaft toward the distal end of the proximal end shaft 11and which has even better kink resistance. In this case, the degree ofgradual decrease in the width 16 of the spiral can be adjusted andoptimized by taking into account the rigidity of proximal end shaft 11and distal end shaft 10. Moreover, the rigidity of distal end portion 13of the proximal end shaft may be also optimized by gradually increasingthe pitch 15 of the spiral as the distal end of the proximal end shaft11 is being approached and by gradually decreasing the width 16 of thespiral as the distal end of the proximal end shaft 11 is beingapproached.

[0087] When the rigidity of the distal end portion 13 of the proximalend shaft is reduced with slits 17, as shown in FIGS. 10 through 13, theslits may be present in either the axial direction or circumferentialdirection of the proximal end shaft. As shown in FIG. 10 and FIG. 11,when the slits are present in the axial direction, a more continuousdistribution of rigidity in the entire catheter shaft can be obtained bychanging the spacing 18, width 19, and length 20 of the slits. When theslits are present in the circumferential direction, as shown in FIG. 12and FIG. 13, the same effect can be produced by changing the spacing 18and width 19 of the slits.

[0088] Further, when the rigidity of the distal end portion 13 of theproximal end shaft is reduced with grooves 21, as shown in FIGS. 14through 18, the grooves 21 may be present in either the axial direction(see FIGS. 14 and 15) or circumferential direction (see FIGS. 16 and 17)of the proximal end shaft or may be in the form of a spiral (see FIG.18). A more continuous distribution of rigidity in the entire cathetershaft can be obtained by changing the width 22, spacing 23, and length24 of the grooves, in the same manner as discussed with reference toslits 17.

[0089] When the rigidity of the distal end portion 13 of the proximalend shaft is reduced with holes 26, as shown in FIG. 19, a morecontinuous distribution of rigidity in the entire catheter shaft can beobtained by changing the shape, size, and spacing of holes 26, in thesame manner as discussed with reference to slits 17 or grooves 21.

[0090] The length of the distal end portion 13 of the proximal end shaft11 is preferably no less than 30 mm. When it is less than 30 mm, changesof the rigidity of the distal end portion 13 of the proximal end shaft11 become abrupt and sufficient kink resistance is difficult to realize.As described above, because the rigidity of the distal end shaft 11 isdetermined by the profile and material, the rigidity of the distal endportion 13 of the proximal end shaft 11 can be optimized by changing thelength of the distal end portion 13 of the proximal end shaft 11. Withconsideration for the profile required for the proximal end shaft 11when the medical balloon catheter is designed for PTCA, it is especiallypreferred that the length of the distal end portion 13 of the proximalend shaft 11 be no less than 0.5 mm and no more than 50 mm.

[0091] A specific feature of the present invention is that the distalend shaft 10 and proximal end shaft 11 are joined outside the distal endportion 13 of the proximal end shaft. The reference symbol 12 in thefigures denotes the joint zone of the distal end shaft 10 and proximalend shaft 11. Spiral notch 14, slits 17, grooves 21, holes 26, or thelike are provided to change continuously the rigidity of the distal endportion 13 of the proximal end shaft 11. In particular, if the distalend shaft 10 is joined in the distal end portion 13 of the proximal endshaft 11, when through passages are made in the wall surface of theproximal end shaft 11, as in the case of spiral notch 14, slits 17, andholes 26, a liquid-tight structure of the inflation lumen 6 of themedical balloon catheter is difficult to obtain and the balloon cannotbe caused to expand or contract.

[0092] No limitation is placed on the method for joining the distal endshaft 10 and proximal end shaft 11. In other words, well-knowntechnology can be used therefor. For example, adhesive bonding with anadhesive or fusion, if the distal end shaft 10 and proximal end shaft 11are fusible, can be used. Furthermore, no limitation is placed on thecomposition, chemical structure or curing system of the adhesive usedfor joining. In other words, in terms of composition and chemicalstructure, adhesives of urethane, silicone, epoxy, cyanoacrylate, andother types can be used. In terms of curing system, adhesives oftwo-liquid mixed type, UV-curable adhesives, adhesives curable by waterabsorption, heat-curable adhesives, radiation-curable adhesives, and thelike can be used. It is preferred that the adhesive have a hardnessafter curing such that the rigidity of the joint zone 12 of the distalend shaft 10 and proximal end shaft 11 do not change discontinuously viathe adhesive bonding zone, and the adhesive can be selected by takinginto account the rigidity of the distal end shaft 10 and proximal endshaft 11.

[0093] In accordance with the present invention, the rigidity of thedistal end shaft 10 is preferably lower than that of the distal endportion 13 of the proximal end shaft. As a result, the distribution ofrigidity in the lengthwise direction of the medical balloon catheter issuch that the rigidity gradually decreases toward the distal end of themedical balloon catheter and a contribution is made to the increase ofkink resistance and, at the same time, to the improvement oftrackability. However, when the rigidity of the distal end shaft 10 istoo low by comparison with that of the distal end portion 13 of proximalend shaft 11, though the distribution of rigidity in the lengthwisedirection of the medical balloon catheter is a gradually decreasing one,the degree of gradual decrease increases. As a result the kinkresistance can be reduced. In such a case, as shown in FIG. 20, therigidity can be adjusted by arranging a core wire 27 inside the distalend shaft 10. The core wire 27 as referred to herein means a membermounted on the proximal end shaft 11, distal end shaft 10, or hub 3 andextending inside the distal end shaft 10 toward the distal end.

[0094] When the rigidity of the distal end shaft 10 is higher than thatof the distal end portion 13 of the proximal end shaft 11, the lowestrigidity of the catheter shaft is in the distal end portion 13 of theproximal end shaft 11 and the distribution of rigidity becomesdiscontinuous. Such a discontinuity not only reduces the kinkresistance, but also causes the decrease in pushability and trackabilityand degrades the performance of the medical balloon catheter as a whole.

[0095] From the standpoint of crossability, it is advantageous that theprofile of the distal end shaft 10 be as small as possible, but theprofile has to be determined by taking into account the rigidity, crosssectional area of inflation lumen 6, cross sectional area of guidewirelumen 4, diameter of the guidewire used in the catheter, and the like.The profile changes depending on the usage and application of themedical balloon catheter, but the outer diameter is 0.75-3.00 mm,preferably, 0.80-2.50 mm.

[0096] Similarly, from the standpoint of crossability, it isadvantageous that the profile of the proximal end shaft 11 be as smallas possible, but the profile has to be determined by taking into accountthe rigidity distribution, cross sectional area of inflation lumen 6,and the like. The profile changes depending on the usage and applicationof the medical balloon catheter, but the outer diameter is 0.55-2.00 mm,preferably, 0.60-1.50 mm.

[0097] Dipping molding, blow molding, and the like are used as methodfor the manufacture of balloon 2 that can be inflated or contracted byinternal pressure adjustment and is provided on the distal end of thedistal end shaft 10, and the appropriate method can be selectedaccording to the usage and application of the medical balloon catheter.In case of medical balloon catheters designed for dilatotherapy ofstenotic portions of blood vessels or body cavities, blow molding ispreferred because it provides for sufficient resistance to pressure. Asan example, first, a tubular parison of any size is molded by extrusionmolding or the like. This tubular parison is placed in a die having amold matching in shape the balloon and stretched in the axial directionand radial direction by a biaxial stretching process. To mold a balloonof the same shape as that of the die. The biaxial stretching process maybe conducted under heating or repeated several times. Furthermore, axialstretching and radial stretching may be conducted simultaneously orsequentially. Further, the balloon may be subjected to annealing tostabilize the shape and size of the balloon.

[0098] The balloon 2, as shown in FIG. 2 and FIG. 3, comprises astraight tubular portion 2 a and joining portions 2 b, 2 b forconducting liquid-tight joining at the distal end side and proximal endside of the straight tubular portion. Tapered portions 2 c are providedbetween the straight tubular portion 2 a and joining portions 2 b. Thesize of balloon 2 is determined by the usage and application of themedical balloon catheter. The outer diameter of straight tubular portion2 a in the balloon inflated by the internal pressure adjustment is1.50-35.00 mm, preferably 1.50-30.00, and the length of straight tubularportion 2 a is 10.00-80.00 mm, preferably, 10.00-60.00 mm.

[0099] No limitation is placed on the resin material of the tubularparison. Examples of suitable materials include polyolefins, polyolefinelastomers, polyesters, polyester elastomers, polyamides, polyamideelastomers, polyurethanes, polyurethane elastomers, and the like.Blended materials prepared by blending two or more of those resinmaterials or multilayer structures obtained by lamination of two or morethereof may be also used.

[0100] No limitation is placed on the material of the proximal end shaft11. Examples of suitable materials include polyolefins, polyolefinelastomers, polyesters, polyester elastomers, polyamides, polyamideelastomers, polyurethanes, polyurethane elastomers, polyimides,polyimidoamides, polyetherimides, polyetherketones,polyetheretherketones, metals of a variety of types, and the like.However, when a balance of continuity of rigidity distribution in theentire medical balloon catheter, pushability, trackability, and the likeis taken into account, it is preferred that a metal tube be used. Fromthe standpoint of production cost, it is more preferred that the metalbe a stainless steel tube, and with consideration for rigidity of theproximal end shaft 11 itself, it is even more preferred that stainlesssteel SUS316 be used. Further, when the above-mentioned resin materialsare used for the proximal end shaft 11, the rigidity may be adjusted byarranging a core wire 27 inside the proximal end shaft 11 or in theproximal end shaft 11 and distal end shaft 10 to provide for thecontinuity of rigidity distribution in the entire medical ballooncatheter.

[0101] No limitation is placed on the material of tubes constituting thedistal end shaft 10. When the distal end shaft 10 has a coaxialstructure, polyolefins, polyolefin elastomers, polyesters, polyesterelastomers, polyamides, polyamide elastomers, polyurethanes,polyurethane elastomers, and the like can be used for the inner tube 7.When the distal end shaft has a coaxial structure, because the guidewirelumen 4 is demarcated by the inner surface of the inner tube 7, from thestandpoint of guidewire slidability it is preferred that polyethylene,in particular, high-density polyethylene, be used. The inner tube 7 canalso have a multilayer structure, with the innermost layer being fromhigh-density polyethylene and the outermost layer being from a materialthat can be adhesively bonded with or fused with the balloon 2. In orderto improve further the guidewire slidability, a lubricating coating ofsilicone, Teflon, or the like can be provided on the inner surface ofinner tube 7.

[0102] No limitation is placed on the material of outer tube 8. Thus,polyolefins, polyolefin elastomers, polyesters, polyester elastomers,polyamides, polyamide elastomers, polyurethanes, polyurethaneelastomers, and the like, can be used.

[0103] Further, even when the distal end shaft 10 has a biaxialstructure or any other structure, materials suitable for theabove-described inner tube 7 or outer tube 8 can be used.

[0104] Resins such as polycarbonates, polyamides, polyurethanes,polysulfones, polyallylates, styrene-butadiene copolymers, polyolefins,and the like can be advantageously used as the material constituting thehub 3.

[0105] In order to improve visibility of balloon 2 under X ray imagingand to facilitate positioning of the balloon in the target zone ofpathological changes, an X ray impermeable ring 9 may be provided on theouter surface of the distal end shaft present inside the balloon. The Xray impermeable ring 9 may be of any material with X ray impermeability,and metals or resins may be used for the ring. No limitation is alsoplaced on the position and number of such rings and they can be setaccording to the target usage of the medical balloon catheter.

[0106] A hydrophilic coating can be provided on the outer surface of themedical balloon catheter to facilitate the insertion into blood vesselsor guide catheter. Thus, a hydrophilic coating providing lubricationduring contact with blood to zones which are in contact with blood ispreferably provided on the outer surface of distal end shaft 10, outersurface of proximal end shaft 11, outer surface of balloon 2, and thelike. No limitation is placed on the type of such hydrophilic coating,but hydrophilic polymers such as poly(2-hydroxyethyl methacrylate),polyacrylamide, polyvinyl pyrrolidone, or the like can be advantageouslyused. No limitation is placed on the coating method.

[0107] Depending on the target usage of the medical balloon catheter, ahydrophobic coating can be provided on the outer surface of balloon 2 inorder to prevent slipping in the zone of pathological changes duringinflation of balloon 2. No limitation is placed on the type of suchhydrophobic coating. Hydrophobic polymers such as silicones can beadvantageously used for the coating.

[0108] An embodiment relating to the structure of the distal end portionincluding the balloon of the medical balloon catheter in accordance withthe present invention will be explained below with reference to FIGS. 23through 28, but the present invention is not limited thereto. Thepresent invention relates to a balloon catheter composed of a pluralityof tubes. FIGS. 23 and 24 illustrate an example in which the distal endportion comprises a balloon of the balloon catheter in accordance withthe present invention, a tube having a lumen for passing a guidewire andformed so that the outer diameter on the distal end side is smaller thanthat on the proximal end side, and a tip portion.

[0109] Referring to FIG. 23, a tube 41 having a lumen for passing aguidewire is formed so that the outer diameter on the distal end portion43 is smaller than that of the proximal end portion 42 and is arrangedto pass inside the balloon 44. At the distalmost end of the catheter,the tube is coaxially fused, as shown in FIG. 26 (cross sectional viewalong the E-E′ line in FIG. 23) to balloon 44, forming a tip portion.The balloon 44, on the other end thereof, is fused with a tube 45constituting the outer surface of the catheter. The X ray impermeablering 49 is designed so that the inner diameter thereof is larger thanthe outer diameter of the distal end portion 43 of tube 41 and smallerthan the outer diameter of proximal end portion 42. The proximal end ofX ray impermeable ring 49 is abutted onto and fixed to the boundary zonebetween the distal end portion and a small-diameter portion on thedistal end side in tube 41. Referring to FIG. 24, the tube 41 having alumen for passing a guidewire is formed so that the outer diameter ofdistal end portion 43 is less than the outer diameter of the proximalend portion 42 and that the inner diameter of distal end portion 43 isless than the inner diameter of distal end portion 42. Furthermore, tube41 is arranged to pass inside the balloon 44, and at the distalmost endof the catheter, the tube is coaxially fused, as shown in FIG. 26 (crosssectional view along the E-E′ line in FIG. 23) with balloon 44, forminga tip portion. On the other hand, the proximal end of balloon 44 isfused with a tube 45 constituting the outer surface of the catheter.

[0110] The inner diameter on the distal end side of tube 41 formed sothat the outer diameter of distal end portion 43 is less than that of 42may be equal to the inner diameter of proximal end portion, as shown inFIG. 23, or maybe less than the inner diameter of proximal end portion,as shown in FIG. 24.

[0111]FIG. 25 is a cross-sectional schematic view illustrating theentire rapid exchange balloon catheter in accordance with the presentinvention. The rapid exchange balloon catheter as referred to herein istypically a balloon catheter with a structure in which the tube 41 forpassing a guidewire is made short in order to facilitate the exchange ofthe balloon catheter. The present invention is, however, not limited tothe rapid exchange balloon catheters.

[0112] An embodiment of the present invention will be described below ingreater detail. The present invention relates to a balloon cathetercomposed of a plurality of tubes and a balloon, this catheter having astructure in which the tube 41 formed to have an outer diameter on thedistal end side smaller than that of the proximal end side and servingas the tube 41 for passing a guidewire inside thereof is arranged so asto pass inside the balloon and the balloon 44 and the small-diameterportion on the distal end side in the tube 41 are fused together in thevicinity of the distal end of the catheter, wherein the ratio of theouter diameter of the small-diameter portion on the distal end side intube 41 to the outer diameter of the proximal end portion, (outerdiameter of small-diameter portion on the distal end side)/(outerdiameter of proximal end portion), is no less than 0.85. Because fusionis used for fixing the balloon 44 and tube 41, no adhesive layer isformed. As a result, the tip portion is provided with flexibility anddiscontinuity of flexibility therein can be reduced. Furthermore, fromthe standpoint of reducing the diameter and providing for continuity offlexibility, it is preferred that the ratio of the outer diameter of thesmall-diameter portion on the distal end side to the outer diameter ofthe proximal end portion, (outer diameter of small-diameter portion onthe distal end side)/(outer diameter of proximal side portion), be noless than 0.85 and no more than 0.95. Thus, if the ratio less than 0.85,flexibility becomes discontinuous and an adverse effect can be produced.When the ratio is above 0.95, the degree of flexibility enhancement inthe distal end of the catheter owing to diameter reduction is small. Onthe other hand, in addition to the structure shown in FIG. 23 and FIG.24 in which a step is formed between the large-diameter section and asmall-diameter section, a tapered structure with gradually changingdiameter or a structure combining those two structures can be used. Inthis case, the diameter of tube 41 in the vicinity (in the positionshifted by 5 mm from the fusion portion toward the proximal end) of thefusion portion with the distal end side of balloon 44 is used as theouter diameter of the small-diameter portion on the distal end side, anda diameter of tube 41 for passing a guidewire directly below the fusionportion (directly below the center of the fusion portion) of theproximal end side of balloon 44 and tube 45 constituting the outersurface of the catheter is used as the outer diameter of the proximalend portion. Further, from the standpoint of reducing the discontinuityof rigidity, the ratio of the thickness of the small-diameter portion onthe distal end side and the thickness of the proximal end portion ispreferably no less than 0.7, even more preferably, no less than 0.8.

[0113] Further, the present invention relates to a balloon cathetercomposed of a plurality of tubes and a balloon, this catheter having astructure in which the tube 41 formed to have an outer diameter on thedistal end side smaller than that of the proximal end side and servingas the tube 41 for passing a guidewire inside thereof is arranged so asto pass inside the balloon and the balloon 44 and the small-diameterportion on the distal end side in the tube 41 are fused together in thevicinity of the distal end of the catheter, wherein any of the values ofShore hardness, or flexural modulus of elasticity, or melting point atleast of that part of the small-diameter portion on the distal end sidein the tube 41 which is fused with the balloon 44 are less that therespective values of the material constituting the balloon 44. Settingspecific limitations on Shore hardness, flexural modulus of elasticity,and melting point makes it possible to improve further the flexibilityof the guidewire tube itself, in addition to the effect obtained byforming a structure in which the ratio of the outer diameter of thesmall-diameter portion on the distal end side to the outer diameter ofthe portion on the proximal end side is no less than 0.85 and no morethan 0.95, and to provide a balloon catheter with a more flexible distalend.

[0114] Further, the present invention provides a balloon catheter aimedat therapy of coronary artery and composed of a plurality of tubes and aballoon, this catheter having a structure in which the tube 41 formed tohave an outer diameter on the distal end side smaller than that on theproximal end side and serving as the tube 41 for passing a guidewireinside thereof is arranged so as to pass inside the balloon 44 and theballoon 44 and the small-diameter portion on the distal end side in thetube 41 are fused together in the vicinity of the distal end of thecatheter, wherein the outer diameter of the small-diameter portion onthe distal end side in said tube is no more than 0.52 mm. As for theouter diameter of tube 41, in case of catheters for expanding a coronaryartery, the outer diameter of no more than 0.52 mm and no less than 0.49mm is preferred from the standpoint of strength required for the tube41. Thus, if the outer diameter is above 0.52 mm, the degree offlexibility provided to the distal end of catheter is small, and if itis less than 0.49, the problem is associated with the decreasedresistance of the tube to pressure.

[0115] Further, the balloon catheter in accordance with the presentinvention has a structure such that when the balloon 44 is composed of apolyester elastomer material or a polyamide elastomer material, at leastthat part of the small-diameter portion on the distal end side ofguidewire tube 41 which is fused with the balloon 44 is formed of theresin of the same type as the balloon 44, that is from a polyesterelastomer material or a polyamide elastomer material. As a result,fusion, which produces no adhesive layer, can be conducted. Therefore,the diameter of the tip portion can be decreased, flexibility can beimproved, and discontinuity of flexibility can be reduced. Furthermore,in case of a structure in which the above-mentioned polyester elastomermaterials or polyamide elastomer materials have hard segment and softsegment components in a molecule, employing a structure in which theratio of soft segments in the material constituting the balloon 44 isless than the ratio of soft segments in the material constituting thetube 41 for passing a guidewire inside thereof makes it possible toprovide a balloon catheter in which the flexibility of the tube 41itself is increased and the flexibility of the distal end is increased.

[0116] No specific limitation is placed on the inner surface ofguidewire tube 41, and a single-layer tube 41 may be made from the samematerial as the portion fused with the balloon 44, provided that aminimum required guidewire slidability is ensured. However, becausematerials with a low Shore hardness, flexural modulus, and melting pointtypically have poor sliding properties, it is preferred that a materialwith excellent sliding properties, which is different from that of theportion fused with the balloon 44, be arranged on the inner surface, andthe innermost surface is preferably composed of high-densitypolyethylene. Furthermore, to enable fusion with the balloon 44, theportion of the guidewire tube 41, which is to be fused with the balloon44, is preferably composed of a material with excellent fusibility withthe balloon 44. Moreover, when the balloon 44 is composed of a polyesterelastomer, the portion of tube 41 which is to be fused with the balloon44 is preferably composed of a polyester elastomer, and when the balloon44 is composed of a polyamide elastomer, the portion of tube 41 which isto be fused with the balloon 44 is preferably composed of a polyamideelastomer. The portion which is to be fused with balloon 44, as referredto herein, may be located anywhere, provided that it is a portionallowing the two members to be fixed by mixing with the materialconstituting the balloon during fusion and solidifying, but it isespecially preferred that this portion be the outermost layer of thetube 41. With the present structure, the guidewire tube 41 can beprovided with a combination of fusion ability and high guidewireslidability. In this case, a layer of a material for providing the tube41 with described mechanical properties, or a binder layer may bepresent between the innermost layer and the portion which is to be fusedwith the balloon 44, no limitation being placed on the number, type, andthickness ratio of such layers. For example, when a binder layer isformed, the conventional lamination technology and adhesive bondingtechnology can be applied. A safer balloon catheter in which interfacepeeling between the portion which is to be fused with the balloon 44 andthe innermost surface is made difficult can be provided if one or aplurality of materials having a solubility parameter (SP value) betweenthose of the material layers constituting the portion which is to befused with balloon 44 and the innermost surface is arrangedtherebetween, or a material having adhesive properties is arranged onthe portion which is to be fused with balloon 44 and the innermostsurface. When the layer forming the portion which is to be fused withthe balloon 44 is from a thermoplastic elastomer such as a polyesterelastomer or a polyamide elastomer, it is preferred that the calculatedflexural rigidity of the elastomer layer represented by a product of thetensile modulus of the elastomer and the geometrical moment of inertiadetermined by the dimensions and shape of the elastomer layer becontrolled so as to be greater than that of the other layers. Further,as described above, the tube 41 represented in accordance with thepresent invention is often preferred to have a multilayer structure, andthe tube 41 with the entirely multilayer structure can be used, but thetube in which only the small-diameter portion on the distal end side andvicinity thereof has a multilayer structure may be also used. Referringto FIG. 26, the reference symbol 51 stands for a material layeroriginating from balloon 44; 52—material layer originating from theoutermost surface of guidewire tube 41; 53—material layer originatingfrom the binder layer of guidewire tube 41; and 54—material layeroriginating from the innermost surface of guidewire tube 41.

[0117] Further, the present invention provides a balloon catheter aimedat therapy of coronary artery and composed of a plurality of tubes and aballoon, this catheter having a structure in which the tube 41 formed tohave an outer diameter on the distal end side smaller than that on theproximal end side and serving as the tube 41 for passing a guidewireinside thereof is arranged so as to pass inside the balloon 44 and theballoon 44 and the small-diameter portion on the distal end side in thetube 41 are fused together in the vicinity of the distal end of thecatheter, wherein that part of the small-diameter portion on the distalend side in the tube 41 which is to be fused with the balloon 44 iscomposed of a polyester elastomer having hard segments and soft segmentsin a molecule, and the ratio of soft segments is above 13%. From thestandpoint of providing the distal end of catheter with flexibility, itis preferred that the ratio of soft segments of the polyester elastomerforming the part which is to be fused with balloon 44 be above 13%. Thetip portion can be adjusted to a flexible condition by increasingflexibility inherent to guidewire tube 41 and by using fusion, whichproduces no adhesive layer, as a fixing method. On the other hand, it ispreferred that the ratio of soft segments of the polyester elastomerforming the part which is to be fused with the balloon 44 be less than70%, in order to prevent extreme deformation in response to pressureapplied when the balloon 44 is inflated.

[0118] Further, the present invention provides a balloon catheter aimedat therapy of coronary artery and composed of a plurality of tubes and aballoon, this catheter having a structure in which the tube 41 formed tohave an outer diameter on the distal end side smaller than that on theproximal end side and serving as the tube 41 for passing a guidewireinside thereof is arranged so as to pass inside the balloon 44 and theballoon 44 and the small-diameter portion on the distal end side in thetube 41 are fused together in the vicinity of the distal end of thecatheter, wherein that part of the small-diameter portion on the distalend side in the tube 41 which is to be fused with the balloon 44 iscomposed of a polyamide elastomer having hard segments and soft segmentsin a molecule, and the ratio of soft segments is above 14%. From thestandpoint of providing the distal end of catheter with flexibility, itis preferred that the ratio of soft segments of the polyamide elastomerforming the part which is to be fused with balloon 44 be above 14%. Thetip portion can be adjusted to a flexible condition by increasingflexibility inherent to guidewire tube 41 and by using fusion, whichproduces no adhesive layer, as a fixing method. On the other hand, it ispreferred that the ratio of soft segments of the polyamide elastomerforming the part which is to be fused with the balloon 44 be less than70%, in order to prevent extreme deformation in response to pressureapplied when the balloon 44 is inflated.

[0119] In the medical balloon catheter, the X ray impermeable ring 49preferably is abutted against and fixed to the boundary portion of theproximal end side and the small-diameter portion on the distal end sideof the guidewire tube 41. Thus, if the X ray impermeable ring 49 isarranged on the proximal end side which is thicker than the distal endportion 43, the flexibility of the portion where the ring is arrangedwill be further decreased by comparison with that on the distal endside. Moreover, because the X ray impermeable ring 49 is arranged sothat it abuts against the boundary portion on the proximal end side,changes of flexibility from the thick proximal end side to the thindistal end side are smoothed and discontinuity of flexibility can bereduced.

[0120] Further, in accordance with the present invention, a structuremay be also provided in which the tube 41 constituting the outer surfaceof the catheter is composed of a material fusible with the balloon 44and fused with and arranged on the proximal end side of balloon 44.Employing a structure in which the tube 45 constituting the outersurface of the catheter is fused with the proximal end side of balloon44 makes it possible to provide a medical balloon catheter which isflexible and in which discontinuity of flexibility hardly occurs on theproximal end side of balloon 44, because no new adhesive layer isformed.

[0121] Shore hardness indicated in the present invention can be measuredby the method indicated in ASTM D 2240, flexural modulus of elasticitycan be measured by the method indicated in ASTM D 790, and tensilemodulus of elasticity can be measured by the method indicated in ASTM D638. Melting point can be measured by using the conventional DSCmeasurement apparatus. The ratio of hard segments and soft segments inthe materials indicated in the present invention is a weight ratio ofcomponents in the materials and can be measured by NMR.

[0122] (Embodiments of Catheter Shaft)

[0123] The catheter shaft of the medical balloon catheter in accordancewith the present invention will be described below in greater detail,based on specific embodiments and comparative examples thereof, but thepresent invention is not limited thereto.

[0124] (Embodiment 1)

[0125] A tubular parison (inner diameter 0.43 mm, outer diameter 0.89mm) was fabricated by an extrusion molding method by using a polyamideelastomer (trade name: PEBAX7233SA01, manufactured by Elf Atochem Co.).Then, a balloon with an outer diameter of a straight tube portion of 3.0mm was fabricated by a biaxial stretching and blowing method by usingthe parison.

[0126] The inner tube (inner diameter 0.42 mm, outer diameter 0.56 mm)and an outer tube (inner diameter 0.71 mm, outer diameter 0.88 mm) werefabricated by extrusion molding by using a polyamide elastomer (tradename PEBAX7233SA01, manufactured by Elf Atochem Co.). The balloon andouter tube were joined by thermal fusion. Then, the inner tube and outertube were arranged so as to obtain a coaxial double-wall tubularconfiguration and the balloon and inner tube were joined by thermalfusion. Notches with a length of half a perimeter in the circumferentialdirection were provided in part of the outer tube, the inner tube wasthereafter fused in an exposed state to the outer surface of the outertube, and a guidewire port was formed. The product was employed as adistal end shaft—balloon assembly. The outer surface of the balloon wascoated with an aqueous solution of polyvinyl pyrrolidone.

[0127] A proximal end shaft (inner diameter 0.50 mm, outer diameter 0.66mm) was fabricated from a stainless steel SUS316.

[0128] A spiral notch with a width of the spiral of 2 mm and a pitch ofthe spiral of 0.5 mm was formed by laser processing on a distal endportion with a length of 60 mm. The proximal end shaft and the distalend shaft-balloon assembly were arranged as shown in FIG. 7 andadhesively bonded with a two-liquid mixed-type urethane adhesive (tradename UR0531, manufactured by H. B. Fuller Co., Ltd.).

[0129] A hub was fabricated by an injection molding method using apolycarbonate (trade name Makloron 2658, manufactured by Bayer Co.).Once the hub and proximal end shaft have been adhesively joined with atwo-liquid mixed-type urethane adhesive (trade name UR0531, manufacturedby H. B. Fuller Co., Ltd.), the balloon was subjected to lapping and EOGsterilization treatment was conducted.

[0130] (Embodiment 2)

[0131] Fabrication was conducted in the same manner as in Embodiment 1,except that slits with a width of 0.3 mm and a spacing of 2 mm wereprovided with a length of half a perimeter in the circumferentialdirection by laser processing on a distal end portion (with a length of50 mm) of a proximal end shaft, as shown in FIG. 12.

[0132] (Embodiment 3)

[0133] Fabrication was conducted in the same manner as in Embodiment 1,except that four round holes with a diameter of 0.4 mm were producedwith equal spacing on the same circumference by laser processing on adistal end portion (with a length of 40 mm) of a proximal end shaft, thedistance between the holes in the axial direction being 0.5 mm, as shownin FIG. 19.

[0134] (Embodiment 4)

[0135] The distal end portion of the proximal end shaft of Embodiment 1was stretched to obtain a width of the spiral of 2 mm and a pitch of thespiral of 1.6 mm. Upon completion of stretching, fabrication wasconducted in the same manner as in Embodiment 1, except that the distalend portion of the proximal end shaft was cut to a length of 60 mm.

[0136] (Embodiment 5)

[0137] Fabrication was conducted in the same manner as in Embodiment 1,except that, as shown in FIG. 20, the proximal end shaft was fabricatedfrom a thermosetting polyimide, grooves with a width of 0.1 mm, a depthof 0.1 mm, and a spacing of 5 mm were produced by laser processing on adistal end portion (with a length of 70 mm) of a proximal end shaft, acore wire from stainless steel SUS 314 with a diameter of 0.25 mm wasarranged from inside the proximal end shaft to the proximal end side ofdistal end shaft, and the core wire was adhesively bonded and secured tothe outer peripheral surface of inner tube with a two-liquid mixed-typeurethane adhesive (trade name UR0531, manufactured by H. B. Fuller Co.,Ltd.).

COMPARATIVE EXAMPLE 1

[0138] Fabrication was conducted in the same manner as in Embodiment 1,except that no spiral notch of Embodiment 1 was provided in the distalend portion of proximal end shaft.

COMPARATIVE EXAMPLE 2

[0139] Fabrication was conducted in the same manner as in Embodiment 5,except that no groove of Embodiment 5 was provided in the distal endportion of proximal end shaft.

[0140] Embodiments 1 through 5 and Comparative Examples 1, 2 wereevaluated by the following methods.

[0141] (Evaluation 1)

[0142] As shown in FIG. 21 and FIG. 22, an aorta model 29 and a guidecatheter 31 were placed in a water tank 28 filled with a physiologicalsolution at a temperature of 37° C., and a hemostat valve 32 was securedto the guide catheter. The distal end of guide catheter 31 was connectedto a curved plate 33 simulating the coronary artery, and a guidewire 30with a diameter of 0.014″ (about 0.36 mm) was pre-inserted into theguide catheter 31. A polyethylene tube 34 was arranged in the curvedplate 33. The polyethylene tube 34 was composed of a straight portion 36and a curved portion 35. The length of the straight portion 36 was 80mm, the curvature radius of the curved portion 35 was 15 mm, the outerdiameter 37 of the polyethylene tube 34 was 5 mm, and the inner diameter38 thereof was 3 mm. The far end of guidewire 30 was arranged at adistance of 50 mm from the far end of curved plate 33. The operationability was evaluated when a medical balloon catheter was inserted fromoutside the water tank via the hemostat valve along the guidewire 30located inside the guide catheter 31. The evaluation results are shownin Table 1.

[0143] (Evaluation 2) Upon completion of Evaluation 1, the medicalballoon catheter was pushed at a rate of 10 mm/sec to the far endportion of curved plate 33 connected to the distal end of guide catheter31 by using a slide table, and a maximum generated load was measuredwith a digital force gage. The evaluation results are shown in Table 1.

[0144] Evaluation 1 was used to evaluate the kink resistance duringinsertion of the medical balloon catheter into a body from outside ofthe body. Evaluation 2 was mainly used to evaluate the trackability.Therefore, good results of both evaluations are the target effect of thepresent invention.

[0145] In Evaluation 1, good insertion operation ability wasdemonstrated in Embodiments 1 through 5 and kink formation was observedin none of the portions of the catheter shaft when it was passed throughthe hemostat valve.

[0146] On the other hand, in Comparative Examples 1, 2 a kink appearedin the catheter shaft in the distalmost portion of proximal end shaftwhen it passed through the hemostat valve. Kink formation could beprevented by conducting insertion at a very low speed, while graspingthe distalmost portion of the proximal end shaft, but in such a case alarge load was placed on the operator manipulating the medical ballooncatheter and the operation ability could not be considered good.

[0147] In Evaluation 2, no kink appeared during passage through an aortaarc 29 a or curved plate in Embodiments 1 through 5, a maximum loadvalue was from 0.54 N to 0.71 N, and good trackability was demonstrated.

[0148] In Comparative Examples 1, 2 a kink appeared in the distalmostportion of proximal shaft when the distalmost portion of the proximalend shaft reached the vicinity of aorta arc 29 a, and the medicalballoon catheter was difficult to insert from the aorta arc to thedistal end side. Therefore, trackability in Comparative Examples 1, 2was considered to be very poor. TABLE 1 Measurement results on kinkresistance and trackability Evaluation 1 Evaluation 2 Embodiment 1 Goodinsertion operation Maximum generated load ability, no kink appeared0.65 N Embodiment 2 Good insertion operation Maximum generated loadability, no kink appeared 0.60 N Embodiment 3 Good insertion operationMaximum generated load ability, no kink appeared 0.71 N Embodiment 4Good insertion operation Maximum generated load ability, no kinkappeared 0.54 N Embodiment 5 Good insertion operation Maximum generatedload ability, no kink appeared 0.59 N Comparative Kink in the distal endKink in the distalmost Example 1 portion of proximal end portion ofproximal end shaft shaft in aorta arc Comparative Kink in the distal endKink in the distalmost Example 2 portion of proximal end portion ofproximal end shaft shaft in aorta arc

[0149] (Embodiment of Distal End Portion of Catheter)

[0150] More specific embodiments and comparative examples of the distalend portion of the medical balloon catheter in accordance with thepresent invention will be described below. The embodiments describedbelow place no limitation on the present invention.

[0151] (Embodiment 3)

[0152] A rapid exchange balloon catheter for coronary artery with adistal end portion of the catheter shown in FIG. 2 was fabricated bypassing a guidewire tube, in which the layer forming the outermostsurface was composed of a polyester elastomer with a Shore hardness of60 D, a flexural modulus of elasticity of 274 MPa, a melting point of216° C., and soft segment ratio of 22%, the innermost surface wascomposed of a high-density polyethylene, the outer diameter and innerdiameter of the distal end portion were 0.50 mm and 0.40 mm,respectively, and the outer diameter and inner diameter of the proximalend portion were 0.56 mm and 0.42 mm, respectively, inside a balloonwith a rated expansion value of 3.0 mm formed from a polyester elastomerwith a Shore hardness of 72 D, a flexural modulus of elasticity of 568MPa, a melting point of 218° C., and a soft segment ratio of 13% andcoaxially fusing the outer surface of the tube at the distal end of thedistal end side of the balloon. The proximal end of the X rayimpermeable ring was fixed in a position abutting against the boundaryportion of the proximal end side and the small-diameter portion on thedistal end side in the tube. Further, a polyester elastomer was used forthe tube constituting the outer surface of the catheter, and theproximal end side of the balloon and the tube constituting the outersurface of the catheter were joined by fusion. The maximum diameter ofthe tip portion was 0.57 mm and the maximum diameter of the section fromthe tip portion to the balloon portion was 0.77 mm in the zone where thetapered portion of the balloon was folded in the vicinity of theboundary of the tip and balloon.

[0153] (Embodiment 4)

[0154] A rapid exchange balloon catheter for coronary artery with adistal end portion of the catheter shown in FIG. 24 was fabricated bypassing a guidewire tube, in which the layer forming the outermostsurface was composed of a polyamide elastomer with a Shore hardness of55 D, a flexural modulus of elasticity of 196 MPa, a melting point of168° C., and a soft segment ratio of 35%, the innermost surface wascomposed of a high-density polyethylene, the outer diameter and innerdiameter of the distal end portion were 0.51 mm and 0.39 mm,respectively, and the outer diameter and inner diameter of the proximalend portion were 0.56 mm and 0.42 mm, respectively, inside a balloonwith a rated expansion value of 3.0 mm formed from a polyamide elastomerwith a Shore hardness of 70 D, a flexural modulus of elasticity of 430MPa, a melting point of 172° C., and a soft segment ratio of 14% andcoaxially fusing the outer surface of the tube at the distal end of thedistal end side of the balloon. The proximal end of the X rayimpermeable ring was fixed in a position abutting against the boundaryportion of the proximal end side and the small-diameter portion on thedistal end side in the tube. Further, a polyamide elastomer was used forthe tube constituting the outer surface of the catheter, and theproximal end side of the balloon and the tube constituting the outersurface of the catheter were joined by fusion. The maximum diameter ofthe tip portion was 0.56 mm and the maximum diameter of the section fromthe tip portion to the balloon portion was 0.77 mm in the zone where thetapered portion of the balloon was folded in the vicinity of theboundary of the tip and balloon.

COMPARATIVE EXAMPLE 3

[0155] A rapid exchange balloon catheter for coronary artery wasfabricated by passing a tube for passing a guidewire, in which the layerforming the outermost surface was composed of a polyester elastomer witha Shore hardness of 60 D, a flexural modulus of elasticity of 274 MPa, amelting point of 216° C., and a soft segment ratio of 22%, the innermostsurface was composed of a high-density polyethylene, and the outerdiameter and inner were 0.56 mm and 0.42 mm, respectively, inside aballoon with a rated expansion value of 3.0 mm formed from a polyesterelastomer with a Shore hardness of 72 D, a flexural modulus ofelasticity of 568 MPa, a melting point of 218° C., and a soft segmentratio of 13% and coaxially fusing the outer surface of the tube at thedistal end of the distal end side of the balloon. Further, a polyesterelastomer was used for the tube constituting the outer surface of thecatheter, and the proximal end side of the balloon and the tubeconstituting the outer surface of the catheter were joined by fusion.The maximum diameter of the tip portion was 0.63 mm and the maximumdiameter of the section from the tip portion to the balloon portion was0.83 mm in the zone where the tapered portion of the balloon was foldedin the vicinity of the boundary of the tip and balloon.

COMPARATIVE EXAMPLE 4

[0156] A rapid exchange balloon catheter for coronary artery wasfabricated by passing a tube for passing a guidewire, in which the layerforming the outermost surface was composed of a polyamide elastomer witha Shore hardness of 55 D, a flexural modulus of elasticity of 196 MPa, amelting point of 168° C., and a soft segment ratio of 35%, the innermostsurface was composed of a high-density polyethylene, and the outerdiameter and inner diameter were 0.56 mm and 0.42 mm, respectively,inside a balloon with a rated expansion value of 3.0 mm formed from apolyamide elastomer with a Shore hardness of 70 D, a flexural modulus ofelasticity of 430 MPa, a melting point of 172° C., and a soft segmentratio of 14% and coaxially fusing the outer surface of the tube at thedistal end of the distal end side of the balloon. Further, a polyamideelastomer was used for the tube constituting the outer surface of thecatheter, and the proximal end side of the balloon and the tubeconstituting the outer surface of the catheter were joined by fusion.The maximum diameter of the tip portion was 0.62 mm and the maximumdiameter of the section from the tip portion to the balloon portion was0.85 mm in the zone where the tapered portion of the balloon was foldedin the vicinity of the boundary of the tip and balloon.

COMPARATIVE EXAMPLE 5

[0157] A rapid exchange balloon catheter for coronary artery wasfabricated by passing a tube for passing a guidewire, in which the layerforming the outermost surface was composed of a polyester elastomer witha Shore hardness of 72 D, a flexural modulus of elasticity of 568 MPa, amelting point of 218° C., and a soft segment ratio of 13%, the innermostsurface was composed of a high-density polyethylene, and the outerdiameter and inner were 0.56 mm and 0.42 mm, respectively, inside aballoon with a rated expansion value of 3.0 mm formed from a polyesterelastomer with a Shore hardness of 72 D, a flexural modulus ofelasticity of 568 MPa, a melting point of 218° C., and a soft segmentratio of 13% and coaxially fusing the outer surface of the tube at thedistal end of the distal end side of the balloon. Further, a polyesterelastomer was used for the tube constituting the outer surface of thecatheter, and the proximal end side of the balloon and the tubeconstituting the outer surface of the catheter were joined by fusion.The maximum diameter of the tip portion was 0.63 mm and the maximumdiameter of the section from the tip portion to the balloon portion was0.85 mm in the zone where the tapered portion of the balloon was foldedin the vicinity of the boundary of the tip and balloon.

COMPARATIVE EXAMPLE 6

[0158] A rapid exchange balloon catheter for coronary artery wasfabricated by passing a tube for passing a guidewire, in which the layerforming the outermost surface was composed of a polyamide elastomer witha Shore hardness of 70 D, a flexural modulus of elasticity of 430 MPa, amelting point of 172° C., and a soft segment ratio of 14%, the innermostsurface was composed of a high-density polyethylene, and the outerdiameter and inner diameter were 0.56 mm and 0.42 mm, respectively,inside a balloon with a rated expansion value of 3.0 mm formed from apolyamide elastomer with a Shore hardness of 70 D, a flexural modulus ofelasticity of 430 MPa, a melting point of 172° C., and a soft segmentratio of 14% and coaxially fusing the outer surface of the tube at thedistal end of the distal end side of the balloon. Further, a polyamideelastomer was used for the tube constituting the outer surface of thecatheter, and the proximal end side of the balloon and the tubeconstituting the outer surface of the catheter were joined by fusion.The maximum diameter of the tip portion was 0.63 mm and the maximumdiameter of the section from the tip portion to the balloon portion was0.85 mm in the zone where the tapered portion of the balloon was foldedin the vicinity of the boundary of the tip and balloon.

COMPARATIVE EXAMPLE 7

[0159] A commercial rapid exchange balloon catheter for coronary arterywith a rated expansion value of 3.0 mm was used that was manufactured bypassing a tube for passing a guidewire, in which the layer forming theoutermost surface was composed of a polyamide with a melting point of178° C. and the innermost surface was composed of a high-densitypolyethylene, inside a balloon formed from a polyamide with a meltingpoint of 178° C. and coaxially fusing the outer surface of the tube atthe distal end of the distal end side of the balloon. Further, apolyamide elastomer was used for the tube constituting the outer surfaceof the catheter, and the proximal end side of the balloon and the tubeconstituting the outer surface of the catheter were joined by fusion.The maximum diameter of the tip portion was 0.78 mm and the maximumdiameter of the section from the tip portion to the balloon portion was0.89 mm in the zone where the tapered portion of the balloon was foldedin the vicinity of the boundary of the tip and balloon.

COMPARATIVE EXAMPLE 8

[0160] A commercial rapid exchange balloon catheter for coronary arterywith a rated expansion value of 3.0 mm was used that was manufactured bypassing a tube for passing a guidewire, which was composed of apolyamide with a melting point of 176° C. and a soft segment ratio of7%, inside a balloon formed from a polyamide with a melting point of173° C. and a soft segment ratio of 17% and coaxially fusing the outersurface of the tube at the distal end of the distal end side of theballoon. Further, a polyamide elastomer was used for the tubeconstituting the outer surface of the catheter, and the proximal endside of the balloon and the tube constituting the outer surface of thecatheter were joined by fusion. The maximum diameter of the tip portionwas 0.64 mm and the maximum diameter of the section from the tip portionto the balloon portion was 0.82 mm in the zone where the tapered portionof the balloon was folded in the vicinity of the boundary of the tip andballoon.

[0161] Characteristics of guidewire tubes and balloons of various typesused in the above-described Embodiments 3, 4 and Comparative Examples 3through 8 are presented in Table 2 and Table 3, respectively. TABLE 2Characteristics of tubes for passing a guidewire that were used inembodiments and comparative examples Ratio of Shore Flexural Meltingsoft Diameter Diameter Material Material hardness of modulus of point ofsegments in of distal of proximal of of material of material materialmaterial of end side end side outer- inner- outer-most of outer- ofouter- outer-most Outer Inner Outer Inner most most layer most layermost layer layer diam., diam., diam., diam., Units layer layer — MPa °C. % mm mm mm mm GT1 TPEE HDPE 60D 274 216 22 0.50 0.40 0.56 0.42 GT2TPAE HDPE 55D 196 168 35 0.51 0.39 0.56 0.42 GT3 TPEE HDPE 60D 274 21622 0.56 0.42 0.56 0.42 GT4 TPAE HDPE 55D 196 168 35 0.56 0.42 0.56 0.42GT5 TPEE HDPE 72D 568 218 13 0.56 0.42 0.56 0.42 GT6 TPAE HDPE 70D 430172 14 0.56 0.42 0.56 0.42 GT7 PA HDPE 178 0 GT8 TPAE TPAE 176 7

[0162] TABLE 3 Characteristics of balloons used in embodiments andcomparative examples Rated expansion Flexural Ratio value of Shoremodulus of Melting of soft balloon hardness elasticity point segmentsUnits mm Material — MPa ° C. % B1 3.0 TPEE 72D 568 218 13 B2 3.0 TPAE70D 430 172 14 B3 3.0 PA 178 0 B4 3.0 TPAE 173 17

[0163] (Evaluation)

[0164] Comparison of tip portions of Embodiments 3, 4, which are theballoon catheters in accordance with the present invention, with any oftip portions of Comparative Examples 3, 4, 5, 6, 7, and 8 demonstratesthat the tip portions of the embodiments have a smaller maximum diameterwithin a range from the tip to the balloon portion and are moreflexible. Further, discontinuity of flexibility in Embodiments 3 and 4did not seem to be large.

[0165] The balloon catheters of Embodiments 3, 4 and ComparativeExamples, 3, 4, 5, 6, 7, and 8 were tested by passing a balloon catheter55 along a guidewire 57 at a constant rate in the evaluation system(Evaluation 3) shown schematically in FIG. 27, that is, in a constrictedchannel 56 in the model through which the guidewire 57 has been passed,and a load that was applied to the balloon catheter when the balloonpassed through the constricted portion from the tip was measured. Theinner diameter of the constricted portion in the constricted channel 56inside the model was 0.65 mm and the channel was molded from a siliconewith a Shore hardness of 40 D. The measurement was conducted in a statein which the balloon of the balloon catheter was folded on the peripheryof guidewire tube.

[0166] The balloon catheters of Embodiments 3, 4 and ComparativeExamples, 3, 4, 5, 6, 7, and 8 were also tested by passing a ballooncatheter 55 along a guidewire 57 at a constant rate in the evaluationsystem (Evaluation 4) shown schematically in FIG. 28, that is, in acurved channel 60 in a model body fabricated from a polyethylene tubewith an inner diameter of 1.5 mm that was curved at 90 degrees and had acurvature of 5 mm. The channel had a guidewire 57 arranged insidethereof and physiological solution with a temperature adjusted to 37° C.was circulated therein. In the test, a load that was applied to theballoon catheter 55 when the tip portion passed through the curvedportion was measured. The inner surface of the polyethylene tube servingas the curved channel 60 inside the model body was coated with ahydrophilic coating to prevent the effect of the surface state of theballoon catheter.

[0167] The results of Evaluation 3 and Evaluation 4 are presented inTable 4. The results show that the balloon catheters of Embodiments 3, 4in accordance with the present invention could be passed into theconstricted channel 56 in the model body with a load lower than thatrequired in comparative example, had a small diameter of the zone fromthe tip portion to the balloon portion, and had excellent operationability. Those results also show that in the balloon catheters of theembodiments, the balloon catheter tip portions could be passed throughthe curved channel 60 in the model body with a load lower than thatrequired in comparative example, the tip portion were flexible, and thecatheters had excellent operation ability. TABLE 4 Structures ofembodiments and comparative examples and the results obtained withmeasurement systems of Evaluations 3 and 4 Structure of catheter distalend portion Measurement results Guidewire Evaluation 3 Evaluation 4 tubeBalloon Load peak (N) Load peak (N) Embodiment 6 GT1 B1 0.355 0.085Embodiment 7 GT2 B2 0.310 0.077 Comparative GT3 B1 0.638 0.118 Example 3Comparative GT4 B2 0.688 0.098 Example 4 Comparative GT5 B1 0.690 0.333Example 5 Comparative GT6 B2 0.689 0.314 Example 6 Comparative GT7 B31.095 0.343 Example 7 Comparative GT8 B4 0.657 0.265 Example 8

[0168] Industrial Applicability

[0169] In accordance with the present invention, a medical ballooncatheter can be readily provided in which the rigidity of catheter shaftis caused to change continuously in the longitudinal direction of thecatheter shaft and pushability and kink resistance are increased, whilethe profile of a catheter shaft is being held to a minimum andcrossability and trackability are being maintained.

[0170] Further, with the present invention, a medical balloon cathetercan be obtained in which the zone from the tip to the balloon is thin,the flexibility of the tip portion is high and discontinuity offlexibility is small, this medical balloon catheter having excellentoperation ability, in particular, the ability to penetrate into highlyconstricted zones of pathological changes, highly curved zones ofpathological changes, and very hard zones of pathological changes.

1. A medical balloon catheter comprising a catheter shaft composed of adistal end shaft and a proximal end shaft, a balloon on the distal endof said distal end shaft, and a hub provided with a port for supplyingpressure fluid to said balloon on the proximal end of said proximal endshaft, wherein said distal end shaft comprises a guidewire lumen and aninflation lumen for dilating said balloon on the inner surface, saidproximal end shaft is composed of a single member and at the same timecomprises said inflation lumen on the inner surface, the distal endportion of said proximal end shaft has a rigidity lower than other partsof said proximal end shaft, and said distal end shaft and said proximalend shaft are joined together outside of the distal end portion of saidproximal end shaft.
 2. The medical balloon catheter according to claim1, wherein part of the distal end portion of said proximal end shaftoverlaps said guidewire lumen.
 3. The medical balloon catheter accordingto claim 1, wherein the rigidity of the distal end portion of saidproximal end shaft gradually decreases as it moves to the distal endside of said proximal end shaft.
 4. The medical balloon catheteraccording to claim 1, wherein said distal end shaft has a rigidity lowerthan that of the distal end portion of said proximal end shaft.
 5. Themedical balloon catheter according to any of claims 1 through 4, whereina spiral notch is provided on the distal end portion of said proximalend shaft.
 6. The medical balloon catheter according to claim 5, whereinthe pitch of said spiral is no more than 5 mm.
 7. The medical ballooncatheter according to claim 5, wherein the pitch of said spiral is nomore than 2 mm.
 8. The medical balloon catheter according to claim 7,wherein the pitch of said spiral gradually increases toward the distalend side of said proximal end shaft.
 9. The medical balloon catheteraccording to claim 5, wherein the width of said spiral is no less than0.5 mm and no more than 10 mm.
 10. The medical balloon catheteraccording to claim 5, wherein the width of said spiral is no less than0.5 mm and no more than 5 mm.
 11. The medical balloon catheter accordingto claim 10, wherein the width of said spiral gradually decreases towardthe distal end side of said proximal end shaft.
 12. The medical ballooncatheter according to claim 5, wherein the pitch of said spiralgradually increases toward the distal end side of said proximal endshaft and the width of said spiral gradually decreases toward the distalend side of said proximal end shaft.
 13. The medical balloon catheteraccording to any of claims 1 through 4, wherein slits are provided onthe distal end portion of said proximal end shaft.
 14. The medicalballoon catheter according to claim 13, wherein said slits are presentalong the axial direction of said proximal end shaft.
 15. The medicalballoon catheter according to claim 13, wherein said slits are presentalong the circumferential direction of said proximal end shaft.
 16. Themedical balloon catheter according to any of claims 1 through 4, whereingrooves are provided on the distal end portion of said proximal endshaft.
 17. The medical balloon catheter according to claim 16, whereinsaid grooves are present along the axial direction of said proximal endshaft.
 18. The medical balloon catheter according to claim 16, whereinsaid grooves are present along the circumferential direction of saidproximal end shaft.
 19. The medical balloon catheter according to any ofclaims 1 through 4, wherein holes are provided on the distal end portionof said proximal end shaft.
 20. The medical balloon catheter accordingto claim 19, wherein the length of the distal end portion of saidproximal end shaft is no less than 30 mm.
 21. The medical ballooncatheter according to claim 19, wherein the length of the distal endportion of said proximal end shaft is no less than 50 mm.
 22. Themedical balloon catheter according claim 21, wherein said proximal endshaft is composed of a metal tube.
 23. The medical balloon catheteraccording to claim 21, wherein said proximal end shaft is composed ofstainless steel.
 24. The medical balloon catheter according to claim 23,wherein said proximal end shaft is composed of stainless steel SUS316.25. The medical balloon catheter according to claim 24, wherein a corewire is provided inside said catheter shaft.
 26. A medical ballooncatheter composed of a plurality of tubes and a balloon, this catheterhaving a structure in which a tube formed to have an outer diameter onthe distal end side smaller than that on the proximal end side andserving as a tube for passing a guidewire inside thereof is arranged soas to pass inside the balloon and the balloon and the small-diameterportion on the distal end side in said tube are fused together in thevicinity of the distal end of the catheter, wherein the ratio of theouter diameter of the small-diameter portion on the distal end side insaid tube to the outer diameter of the proximal end portion, (outerdiameter of the small-diameter portion on the distal end side)/(outerdiameter of the proximal end portion), is no less than 0.85.
 27. Amedical balloon catheter composed of a plurality of tubes and a balloon,this catheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in said tube are fusedtogether in the vicinity of the distal end of the catheter, wherein theShore hardness of the material constituting at least that part of thesmall-diameter portion on the distal end side in said tube which isfused to the balloon is less than the Shore hardness of the materialconstituting the balloon.
 28. A medical balloon catheter composed of aplurality of tubes and a balloon, this catheter having a structure inwhich a tube formed to have an outer diameter on the distal end sidesmaller than that on the proximal end side and serving as a tube forpassing a guidewire inside thereof is arranged so as to pass inside theballoon and the balloon and the small-diameter portion on the distal endside in said tube are fused together in the vicinity of the distal endof the catheter, wherein the flexural modulus of elasticity of thematerial constituting at least that part of the small-diameter portionon the distal end side in said tube which is fused to the balloon isless than the flexural modulus of elasticity of the materialconstituting the balloon.
 29. A medical balloon catheter composed of aplurality of tubes and a balloon, this catheter having a structure inwhich a tube formed to have an outer diameter on the distal end sidesmaller than that on the proximal end side and serving as a tube forpassing a guidewire inside thereof is arranged so as to pass inside theballoon and the balloon and the small-diameter portion on the distal endside in said tube are fused together in the vicinity of the distal endof the catheter, wherein the melting point of the material constitutingat least that part of the small-diameter portion on the distal end sidein said tube which is fused to the balloon is lower than the meltingpoint of elasticity of the material constituting the balloon..
 30. Amedical balloon catheter composed of a plurality of tubes and a balloon,this catheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in said tube are fusedtogether in the vicinity of the distal end of the catheter, wherein theouter diameter of the small-diameter portion on the distal end side insaid tube is no more than 0.52 mm.
 31. The medical balloon catheteraccording to any of claims 26 through 30, wherein the balloon iscomposed of a polyester elastomer material and at least that part of thesmall-diameter portion on the distal end side in said tube for passing aguidewire inside thereof, which is fused to the balloon is composed of apolyester elastomer material.
 32. The medical balloon catheter accordingto any of claims 26 through 30, wherein the balloon is composed of apolyamide elastomer material and at least that part of thesmall-diameter portion on the distal end side in said tube for passing aguidewire inside thereof, which is fused to the balloon is composed of apolyamide elastomer material.
 33. The medical balloon catheter accordingto claim 31 wherein the polyester elastomer material or the polyamideelastomer material has soft segments and hard segments in a molecule andthe ratio of soft segments in the material constituting the balloon isless than the ratio of soft segments in the material constituting thetube for passing a guidewire inside thereof.
 34. The medical ballooncatheter according to claim 33, wherein at least the innermost surfaceof the tube for passing a guidewire inside thereof is composed ofhigh-density polyethylene.
 35. The medical balloon catheter according toclaim 34, wherein the tube for passing a guidewire inside thereof has amultilayer structure consisting of no less than two layers, the portionwhich is to be fused is composed of a polyamide elastomer or a polyesterelastomer, the innermost surface is composed of high-densitypolyethylene, and no less than one binder layer is present, ifnecessary, between the portion that has been fused and the innermostsurface.
 36. A medical balloon catheter composed of a plurality of tubesand a balloon, this catheter having a structure in which a tube formedto have an outer diameter on the distal end side smaller than that onthe proximal end side and serving as a tube for passing a guidewireinside thereof is arranged so as to pass inside the balloon and theballoon and the small-diameter portion on the distal end side in saidtube are fused together in the vicinity of the distal end of thecatheter, wherein that part of the small-diameter portion on the distalend side in said tube which is fused to the balloon is composed of apolyester elastomer having hard segments and soft segments in a moleculeand the ratio of the soft segments is higher than 13%.
 37. A medicalballoon catheter composed of a plurality of tubes and a balloon, thiscatheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in said tube are fusedtogether in the vicinity of the distal end of the catheter, wherein thatpart of the small-diameter portion on the distal end side in said tubewhich is fused to the balloon is composed of a polyamide elastomerhaving hard segments and soft segments in a molecule and the ratio ofthe soft segments is higher than 14%.
 38. The medical balloon catheteraccording to claim 37, wherein the proximal end of an X ray impermeablering is abutted against and fixed to the boundary portion of theproximal end side and the small-diameter portion on the distal end sideof the tube for passing a guidewire inside thereof.
 39. The medicalballoon catheter according to claim 38, wherein the tube constitutingthe outer surface of the catheter is composed of a material that can befused with the balloon and is fused and arranged on the proximal endside of the balloon.